1. Field of the Invention
The present invention relates to a digital TV based on advanced television systems committee (ATSC) standards, and more particularly to a local digital TV signal generator which generates an ATSC radio frequency(RF) signal capable of being received by the digital TV.
2. Discussion of Related Art
In a TV transmitting mode, national television standards committee (NTSC) mode has been adapted for several tens of years. With the introduction of a digital TV recently, the NTSC mode and the digital TV will coexist for several years in the future. There are north American standards and European standards in the digital TV. The north American standards are adapted to the ATSC standards.
In Korea, the ATSC standards have been adapted, and development of appliances related to the digital TV adapted to the ATSC standards is in progress. Therefore, manufacturers of the appliances related to the digital TV adapted to the ATSC standards are requested to manufacture an ATSC RF signal generator for generating an RF signal of the ATSC standards required for development, test, after service and demonstration of sets.
FIG. 1 shows an example of a related art ATSC RF signal generator. Referring to FIG. 1, an RF signal of the ATSC standards is generated using an MPEG test streamer (MTS), a vestigial side band (VSB) modulator, and an RF up-converter. That is to say, the MTS analyzes data compressed with the MPEG and generates MPEG2 streams. As an example, a first byte of the MPEG2 compressed streams always starts at 0xc3x9747, and 188 bytes constitute one packet.
A The VSB modulator performs error correction for the MPEG2 compressed streams, reed-solomon(RS) coding, and DC interpolation, so that a VSB intermediate frequency (IF) signal is generated. That is, when a side band of two side bands is largely offset, the VSB modulator modulates the other side band signal only. The side bands occur up and down based on carriers when the amplitude of the signal is modulated. In case of the ground wave, 8VSB modulation mode is adapted.
The RF up-converter converts the VSB IF signal to a desired RF band signal and then sends the converted signal to a cable or a public wave through an RF cable or antenna.
However, the related art ATSC RF signal generator has problems in that it is expensive and complicate in view of various aspects such as installation and use. That is, the related art ATSC RF signal generator costs several hundred millions won and is too big to carry, thereby further complicating the installation and use.
Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art.
An object of the present invention is to provide a local digital TV signal generator having the low cost and a small size suitable for test or demonstration by generating an RF signal of ATSC standards based on a memory device and a VSB remodulator.
Another object of the present invention is to provide a local digital TV signal generator which stores a VSB signal and converts the VSB signal to an RF signal of ATSC standards if desired.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, a local digital TV signal generator according to the present invention includes a data memory device for storing data required for digital broadcasting in a memory device and outputting the data stored in the memory device through an input/output(I/O) card, a VSB modulator for VSB modulating input data to output an RF signal, and a controller for synchronizing a clock between the data memory device and the VSB modulator, converting the data output from the data memory device to conform to data input format of the VSB modulator to be output to the VSB modulator, and generating a required control signal.
The memory device of the data memory device stores MPEG compressed streams.
The data memory device further includes a data outputting unit for reading out MPEG compressed streams stored in the memory device, adding a parity of a predetermined byte and a field synchronization to the MPEG compressed streams, and converting streams of ATSC standards.
The memory device of the data memory device stores streams of ATSC standards in which a parity of a predetermined byte and a field synchronization are added to the MPEG compressed streams.
The clock supplied from the controller to the data memory device is determined by a VSB mode.
The clock supplied from the controller to the data memory device is determined by the number of data bytes converted if a serial conversion of data output in parallel from the data memory device is required.
In another aspect, a local digital TV signal generator according to the present invention includes an ATSC signal outputting unit for reading out MPEG compressed streams from a memory device which stores the MPEG compressed streams if a data request is input, converting the MPEG compressed streams to streams of ATSC standards, and outputting the streams through an I/O card, a VSB remodulator for VSB modulating input data to output an RF signal, and an RF signal generator which includes a controller for synchronizing a clock between the ATSC signal outputting unit and the VSB modulator, converting the data output from the ATSC outputting unit to conform to data input format of the VSB remodulator to be output to the VSB remodulator, and generating a required control signal.
The memory device of the ATSC signal outputting unit is a hard disk, and a buffer for performing double buffering is further provided between the hard disk and the I/O card.
The controller of the RF signal generator converts M byte data (M is 2 or more) to N byte data (N is 1 or more) and outputs the converted data to the VSB remodulator, if the M byte data is output from the ATSC signal outputting unit and N byte data is input to the VSB remodulator.
In still another aspect, a local digital TV signal generator according to the present invention includes a downloading unit for downloading data from an external device which stores digital broadcasting data, a memory device for storing the downloaded data, a VSB modulator for VSB modulating the data stored in the memory device to output an RF signal, and an RF signal generator which includes a controller for controlling reading of the downloaded data and the data stored in the memory device.
The memory device is a nonvolatile memory device which enables reading and writing operations.
The external device is a hard disk mounted in a general PC, and outputs transport streams coded according to ATSC standards.
The external device is a DVD mounted in a general PC.
In further another aspect, a local digital TV signal generator according to the present invention includes a memory device for storing transport streams encoded by MPEG algorithm, a VSB signal processor for VSB modulating the data stored in the memory device to output an RF signal, a VSB modulator for reading out the transport streams stored in the memory device if desired and VSB modulating them to output the RF signal, and a controller for synchronizing a clock between the memory device and the VSB modulator and converting the data output from the memory device to conform to data input format of the VSB modulator to be output to the VSB modulator.
The memory device is a hard disk mounted in a general PC.
The memory device is a DVD mounted in a general PC.
In other aspect, a local digital TV signal generator according to the present invention includes a demodulator for receiving a digital broadcasting signal from a broadcasting station, VSB demodulating the digital broadcasting signal, and outputting the demodulated signal to transport streams, an audio/video signal processor for dividing an audio signal and a video signal from the transport streams output from the demodulator so that the audio signal is audio-decoded using AC-3 algorithm and the video signal is video-decoded using MPEG2 algorithm, a memory device for storing the transport streams output from the demodulator, a VSB modulator for VSB modulating the transport streams stored in the memory device to output an RF signal, and a controller for converting the transport streams output from the demodulator to a memory type to be stored in the memory device, reading out the transport streams stored in the memory device to conform to data input format of the VSB modulator to be output to the VSB modulator.
The other blocks except the memory device are designed in at least one or more PC cards and can be mounted inside a PC.
The other blocks except the memory device are designed in a separate set top box and can be mounted outside a PC.